The primary objective of this project is characterization of electron transport systems of parasites. Current areas of concentrated effort are electron transport systems of malarial parasites and Entamoeba histolytica. Major compounds of interest are cytochromes and iron-sulfur proteins. The presence of cytochromes are detected by optical spectrophotometry, especially low-temperature spectrophotometry. Iron-sulfur proteins are detected by electron paramagnetic resonance. The importance of iron-sulfur proteins to electron transport in E. histolytica suggests a nutritional requirement for iron and sulfur in the amoeba. We are attempting to improve axenic growth of the amoeba in less complex culture media by the addition of iron and sulfur containing compounds. In addition, studies are done on improving in vivo infectivity of the amoeba in laboratory animals by concurrent administration of iron-containing compounds.